WO2009115540A2

WO2009115540A2 - Polyurethane systems for producing polyurethane sandwich parts at low molding temperatures

Info

Publication number: WO2009115540A2
Application number: PCT/EP2009/053171
Authority: WO
Inventors: Michael Fader
Original assignee: Basf Se
Priority date: 2008-03-20
Filing date: 2009-03-18
Publication date: 2009-09-24
Also published as: CA2717054A1; ATE548401T1; EP2257580A2; KR101663327B1; US8465840B2; CA2717054C; WO2009115540A3; US20110014480A1; KR20110007116A; CN101977954B; CN101977954A; MX2010009337A; EP2257580B1

Abstract

The present invention relates to the use of a polyurethane system comprising (a) polyisocyanates, (b) at least one compound that is reactive to isocyanate, (c) at least one carboxylic acid salt of an amine catalyst, containing 0.5 to 1.5 acid group equivalents of a carboxylic acid, based on an amine equivalent of the amine catalyst, (d) alternatively other catalysts, (e) alternatively a reactive chain extender with at least two groups that are reactive to isocyanates, wherein at least one group that is reactive to isocyanates is a free group, primarily an NH₂ group, and (f) alternatively other additives for producing polyurethane sandwich parts. The present invention further relates to a method for producing polyurethane sandwich parts and the polyurethane sandwich parts obtained according to the method according to the invention.

Description

Polyurethane systems for the production of polyurethane sandwich parts at low mold temperatures.

description

The present invention relates to the use of a polyurethane system comprising (a) polyisocyanates, (b) at least one isocyanate-reactive compound, (c) at least one carboxylic acid salt of an amine catalyst, wherein, based on one equivalent of amine of the amine catalyst, from 0.5 to 1, (E) optionally a reactive chain extender having at least two isocyanate-reactive groups, wherein at least one isocyanate-reactive group is a free, primary Nhb group, and (f) optionally other additives for the production of polyurethane sandwich parts. Furthermore, the present invention relates to a process for the production of polyurethane sandwich parts and the polyurethane sandwich parts obtained by the process according to the invention.

Further embodiments of the present invention can be taken from the claims, the description and the examples. It is understood that the features mentioned above and those yet to be explained of the subject matter according to the invention can be used not only in the particular combination specified, but also in other combinations, without departing from the scope of the invention.

Polyurethane sandwiches have long been known. These are made by covering a core layer with a reinforcing layer. On this so-called sandwich semi-finished product, a polyurethane reaction mixture is applied on one side, in many cases also on two sides, preferably by spraying. Subsequently, the part covered with the polyurethane reaction mixture, the raw sandwich part, is placed in a mold in which the sandwich semi-finished product is press-formed into a certain shape by the thermal compression molding process and the polyurethane reaction mixture is cured into the polyurethane. In this case, the reinforcing layer is compressed during the pressing. The compression can be varied within a wide range and take place from a few tenths of a millimeter to a compression to a few percent of the initial thickness in some sub-areas. Then, the polyurethane sandwich part thus obtained is demolded. In this case, the design of the outer contour via a squeezing of the sandwich package in the forming tool.

In order for a three-dimensional shaping to be possible, the curing of the polyurethane reaction mixture may only take place in the mold. In particular in the area of the edges of such compressed regions, the core layer can only be sealed by polyurethane if, after compression, there is still sufficient flowable polyurethane reaction mixture to cover these regions. Such For example, in the brochure "PUR - Fiber composite materials for lightweight construction in the vehicle interior of Bayer AG Leverkusen (order number: PU 52248) or" Baypreg F - PUR plus nature in the automobile, composite materials made of polyurethane "of Bayer AG Leverkusen.

The problem with the known method is that the molding must be carried out at molding temperatures of about 120 to 140 ⁰ C to ensure the necessary for industrial purposes short demolding, without the necessary for the production of raw sandwich part processing time of the polyurethane system, the These high mold temperatures, however, result in high energy consumption in the production of the polyurethane sandwich part, moreover, direct lamination is only possible with very expensive, heat-resistant decorative materials possible.

The object of the present invention was to reduce the energy consumption and improve the direct lamination behavior in the production of polyurethane sandwich parts, without a shortening of the open time or an extension of the demolding times in comparison to known methods.

The object according to the invention is achieved by the use of a polyurethane system comprising (a) polyisocyanates, (b) at least one isocyanate-reactive compound, (c) at least one carboxylic acid salt of an amine catalyst, based on one equivalent of amine of the amine catalyst, from 0.5 to (D) optionally further catalysts, (e) optionally a reactive chain extender having at least two isocyanate-reactive groups, wherein at least one isocyanate-reactive group is a free, primary NH 2 group , and (f) optionally further additives, for the production of polyurethane sandwich parts.

In the context of the invention, a polyurethane system is to be understood as meaning a system comprising at least two components, the polyurethane reaction mixture according to the invention being obtained on mixing the components. Frequently, components (b) to (f) are combined to form a so-called polyol component, and component (a) is referred to as the isocyanate component.

The polyisocyanates used are preferably aromatic isocyanates. Preferably, aromatic isocyanates of the general formula R (NCO) _Z are used, wherein R is a polyvalent organic radical having an aromatic, and z is an integer of at least 2. Examples include 4,4'-diisocyanatobenzene, 1, 3-diisocyanato-o-xylene, 1, 3-diisocyanato-p-xylene, 1, 3-diisocyanato-m-xylene, 2,4-diisocyanato-1-chlorobenzene, 2,4-diisocyanato-1-nitro-benzene, 2,5-diisocyanato-1 - nitrobenzene, m-phenylene diisocyanate, p-phenylene diisocyanate, 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, mixtures of 2,4- and 2,6-toluene diisocyanate, 1,5-naphthalene diisocyanate, 1-methoxy-2,4-phenylene diisocyanate , 4,4'-diphenylmethane diisocyanate, 2,4'-diphenylmethane diisocyanate, 4,4'-biphenylene diisocyanate, 3,3'-dimethyl-4,4'-diphenylmethane diisocyanate, and 3,3'-dimethyldiphenylmethane-4,4 ' - diisocyanate; Triisocyanates, such as 4,4 ', 4 "-triphenylmethane triisocyanate and 2,4,6-toluene triisocyanate, and tetraisocyanates, such as 4,4'-dimethyl-2,2'-5,5'-diphenylmethane tetraisocyanate. Particularly preferred are toluene diisocyanates , 2,4'-diphenylmethane diisocyanate, 4,4'-diphenylmethane diisocyanate, polymethylene polyphenylene polyisocyanate, as well as derivatives and mixtures thereof.

Preference is given to using higher-nuclear isocyanates, particularly preferably polymethylene polyphenylene polyisocyanate, also referred to as polymer MDI. These can also be prepolymerized before use with polyetherols or polyesterols to Isocyanatprepolymeren to adjust special properties. Furthermore, the use of raw MDI is possible.

In particular, reaction products of polymer MDI and polyesterols, as described under (b), are used as a modified multivalent isocyanate. The isocyanate component has functionalities of 1.2 to 3.0, preferably 1.5 to 3.0, particularly preferably 2.0 to 2.8.

As the isocyanate-reactive compound (b), any compound which can be used in polyurethane production with at least two isocyanate-reactive hydrogen atoms can be used. The isocyanate-reactive compound (b) used is preferably a polyether polyol, a polyester polyol, an amine-functionalized compound or mixtures thereof. Particularly preferred are polyether polyols.

Suitable polyether polyols can be prepared by known processes, for example by anionic polymerization with alkali metal hydroxides, such as sodium or potassium hydroxide, or alkali metal, such as sodium, sodium or potassium, or Kaliu- misopropylate as catalysts and with the addition of at least one starter molecule, the 2 to 8 reactive hydrogen atoms or prepared by cationic polymerization with Lewis acids, such as antimony pentachloride and borofluoride etherate, or bleaching earth as catalysts of one or more alkylene oxides having 2 to 4 carbon atoms in the alkylene radical. Further, as catalysts, it is also possible to use multimetal cyanide compounds, so-called DMC catalysts.

Suitable alkylene oxides are, for example, tetrahydrofuran, 1, 3-propylene oxide, 1, 2 or 2,3-butylene oxide, styrene oxide and preferably ethylene oxide and 1, 2-propylene oxide. The alkylene oxides can be used individually, alternately in succession or as mixtures.

Suitable starter molecules are, for example: water, organic dicarboxylic acids, such as succinic acid, adipic acid, phthalic acid and terephthalic acid, aliphatic and aromatic, optionally N-mono-, N, N- and N, N'-dialkyl-substituted diamines having 1 to 4 carbon atoms in the alkyl radical, such as optionally mono- and dialkyl-substituted ethylenediamine, diethylenetriamine, triethylenetetramine, 1, 3-propylenediamine, 1, 3 or 1, 4-butylenediamine, 1, 2, 1, 3, 1, 4 , 1, 5 and 1, 6-hexamethylenediamine, phenylenediamines, 2,3-, 2,4- and 2,6-toluenediamine and 4,4'-, 2,4'- and 2,2'-diamino- diphenylmethane.

Also suitable as starter molecules are: alkanolamines, such as ethanolamine, diethanolamine, N-methyl- and N-ethyl-ethanolamine, N-methyl- and N-ethyl-diethanolamine and triethanolamine and ammonia. Preference is given to using polyhydric, especially dihydric to hexahydric alcohols, such as ethanediol, propanediol 1, 2 and 1, 3, diethylene glycol, dipropylene glycol, butanediol 1, 4, hexanediol 1, 6, glycerol, trimethylolpropane, Pentaerythritol, glucose, fructose and sucrose.

The polyether polyols, preferably polyoxyethylene, polyoxypropylene, and polyoxypropylene polyoxyethylene polyols, have an average functionality of from 1.5 to 5.0, preferably from 1.8 to 4.2, and more preferably from 2.0 to 3.5, and number average Molecular weights of preferably 32 to 1500, particularly preferably 60 to 1000 and in particular 60 to 800. The different functionalities are preferably obtained by the use of different initiators.

Also suitable as polyols are polymer-modified polyols, preferably polymer-modified polyesterols or polyetherols, particularly preferably graft polyetherols. This is a so-called polymer polyol, which usually has a content of, preferably thermoplastic, polymers of from 5 to 50% by weight, preferably from 10 to 45% by weight, particularly preferably from 15 to 25% by weight, and in particular 18 to 22 wt .-%, having. These polymer polyesterols are described, for example, in EP-A-250 351 and are usually prepared by free-radical polymerization of suitable olefinic monomers, for example styrene, acrylonitrile, acrylates and / or acrylamide, by transferring the radicals of growing polymer chains to polyesterols or polyetherols , In addition to the graft copolymer, the polymer polyol predominantly contains the homopolymers of the olefins dispersed in unchanged polyesterol.

In a preferred embodiment, the monomers used are acrylonitrile, styrene, in particular exclusively styrene. The monomers are optionally in Presence of further monomers, a macromer, a moderator and using a radical initiator, usually azo or peroxide compounds, polymerized in a polyesterol as a continuous phase.

During radical polymerization, the macromers are incorporated into the copolymer chain. This forms block copolymers with a polyester and a poly-acrylonitrile-styrene block, which act as phase mediators in the interface of continuous phase and dispersed phase and suppress the agglomeration of the polymer polyesterol particles. The proportion of macromers is usually 1 to 15% by weight, based on the total weight of the monomers used to prepare the polymer polyol.

Preferably, the proportion of polymer polyol is greater than 5 wt .-%, based on the total weight of component (b). The polymer polyols may, for example, based on the total weight of component (b), in an amount of 30 to 90

Wt .-%, preferably from 55 to 80 wt .-% contained. Particularly preferably, the polymer polyol is polymer polyesterol or polyetherol.

Carboxylic acid salts of all basic amine catalysts customary for polyurethane production can be used as the carboxylic acid salt of an amine catalyst (c). The carboxylic acid salts of the basic amine catalysts are obtained by mixing the amine catalysts with carboxylic acids. This can be done in a separate step, optionally with the use of a solvent, or by adding the acid and the basic amine catalyst to the polyol component.

Preferably, the carboxylic acid salt of the amine catalyst is obtained by mixing in a separate step carboxylic acid and basic amine catalyst, optionally with heating. Preferably, an alcohol, particularly preferably a dihydric or trihydric alcohol having a molecular weight of less than 120 g / mol, in particular ethylene glycol, is used as the solvent. The carboxylic acid salt of an amine catalyst thus formed can then be combined in a further step with at least the component (b) and optionally one of the components (d), (e) and (f) to the polyol component.

Basic amine catalysts are described, for example, in "Kunststoffhandbuch, Volume 7, Polyurethanes", Carl Hanser Verlag, 3rd edition 1993, Chapter 3.4.1. Examples of these are amidines, such as 2,3-dimethyl-3,4,5,6-tetrahydropyrimidine, tertiary amines, such as triethylamine, tributylamine, dimethylbenzylamine, N-methyl-, N-ethyl-, N-cyclohexylmorpholine, N, N, N ', N'-tetramethylethylenediamine, N, N, N', N'-tetramethylbutanediamine, N, N, N ', N'-tetramethylhexanediamine, pentamethyldiethylenetriamine, tetramethyldiaminoethyl ether, Bis (dimethylaminopropyl) urea, N, N-bis (3-dimethylamino-propyl) -N-isopropanolamine, dimethylpiperazine, 1, 2-dimethylimidazole, 1-azabicyclo- (3,3,0) -octane and preferably 1,4-diazabicyclo- (2,2,2) -octane and alkanolamine compounds, such as triethanolamine, triisopropanolamine, N-methyl- and N-ethyl-diethanolamine , N, N-bis (3-dimethylaminopropyl) -N-isopropanolamine and dimethylethanolamine. In particular, basic amine catalysts are used which have at least one, preferably exactly one, isocyanate-reactive group, such as N, N-bis (3-dimethylaminopropyl) -N-isopropanolamine. The catalysts can be used singly or as mixtures.

The carboxylic acids used are preferably those which have a molecular weight of less than 300 g / mol. Particular preference is given to using saturated and unsaturated aliphatic monocarboxylic acids having 1 to 18 carbon atoms, such as formic acid, acetic acid, cyanoacetic acid or 2-ethylhexanoic acid, aromatic carboxylic acids, aliphatic, saturated and unsaturated dicarboxylic acids having 2 to 16 carbon atoms, or tricarboxylic acids or mixtures thereof. It is also possible to use derivatives of the abovementioned carboxylic acids. Further preferred carboxylic acids used are dicarboxylic acids of the general formula HOOC- (CH 2) _n -COOH, where n is an integer from 2 to 14. Such dicarboxylic acids are generally less corrosive. In particular, adipic acid is used as the carboxylic acid.

The ratio of acid and amine catalyst is chosen such that, based on one equivalent of amine amine catalyst, 0.5 to 1, 5, preferably 0.7 to 1, 3, particularly preferably 0.90 to 1, 10 and in particular 0, 95 to 1, 05 equivalents of acid groups of a carboxylic acid are included.

The carboxylic acid salts of an amine catalyst (c) may, for example, in a concentration of 0.001 to 10 wt .-%, preferably 0.05 to 5 wt .-% and particularly preferably 0.05 to 2 wt .-%, based on the weight of the components (b) to (f).

As further catalysts (d), for example, organic metal compounds, preferably organic tin compounds such as stannous salts of organic carboxylic acids, e.g. Tin (II) acetate, stannous octoate, stannous (II) ethyl hexoate, and stannous laurate and the dialkyltin (IV) salts of organic carboxylic acids, e.g. Dibutyltin diacetate, dibutyltin dilaurate, dibutyltin maleate and dioctyltin diacetate, and also bismuth carboxylates such as bismuth (III) neodecanoate, bismuth 2-ethylhexanoate and bismuth octanoate or mixtures. Preferably, no further catalysts (d) are used.

As reactive chain extender (s) it is possible to use substances which have two isocyanate-reactive groups, the substances having at least one free primary Nhb group. These substances accelerate the polyu- rethanreaktion. The further isocyanate-reactive group may be selected, for example, from a primary amino group, an alcohol group or a thiol group. As the reactive chain extender (e), for example, aliphatic or aromatic amines can be used. The reactive chain extenders (e) can be used individually or in the form of mixtures.

In a particularly preferred embodiment, the reactive chain extenders (e) used are preferably aromatic diamines, in particular toluenediamines or derivatives thereof, such as 3,5-diethyl-tolylene-2,4-diamine.

In a further preferred embodiment, the reactive chain extender (e) is aliphatic and has between the two isocyanate-reactive groups at least two alkylene groups each having one or two carbon atoms, wherein the alkylene groups are each separated from a heteroatom. In particular, the two isocyanate-reactive groups are amino groups. Preferably, the molecular weight of the reactive chain extender (e) in this preferred embodiment is between 100 and 400 g / mol, particularly preferably between 100 and 200 g / mol and in particular between 100 and 150 g / mol. If aliphatic reactive chain extenders are used, in particular triethylene glycol diamine is used as reactive chain extender (e).

The proportion of the reactive chain extender on the polyol component is preferably 0.1 to 10% by weight, particularly preferably 0.3 to 8% by weight, more preferably 0.5 to 5% by weight and in particular 1.5 to 4, 0 wt .-%, based on the total weight of components (b) to (f).

In addition to the reactive chain extenders (e), it is also possible if appropriate to use reactive crosslinkers which have at least one free primary Nhb group, accelerate the polyurethane reaction and have a functionality greater than 2.

In addition to the reactive chain extenders (e) according to the invention, further conventional chain extenders can be used. These are, for example, diols, particular preference is given to monoethylene glycol and butanediol. Very particular preference is given in the context of the invention to mixtures of a reactive chain extender according to the invention and a chain extender consisting of a diol.

Further additives (f) which can be used are blowing agents, additives for thixotroping, fillers, antioxidants, dyes, pigments, optical brighteners and stabilizers against heat, light and / or UV radiation, plasticizers or surface-active substances. Examples of suitable release agents are: reaction products of fatty acid esters with polyisocyanates, salts of amino-containing polysiloxanes and fatty acids, salts of saturated or unsaturated (cyclo) aliphatic carboxylic acids having at least 8 carbon atoms and tertiary amines, and in particular internal release agents such as carboxylic esters and or amides prepared by esterification or amidation of a mixture of montanic acid and at least one aliphatic carboxylic acid having at least 10 carbon atoms with at least difunctional alkanolamines, polyols and / or polyamines having molecular weights of 60 to 400 g / mol, such as For example, in EP 153 639 discloses mixtures of organic amines, metal salts of stearic acid and organic mono- and / or dicarboxylic acids or their anhydrides, as disclosed for example in DE-A-3 607 447, or mixtures of an imino compound, the metal salt of a Carboxylic acid and optionally a carbon acid, as disclosed, for example, in US 4,764,537.

As blowing agents, it is possible to use all blowing agents known for the preparation of polyurethanes. These may include chemical and / or physical blowing agents. Such blowing agents are described, for example, in "Kunststoffhandbuch, Volume 7, Polyurethanes", Carl Hanser Verlag, 3rd edition 1993, Chapter 3.4.5. Chemical blowing agents are compounds which form gaseous products by reaction with isocyanate. Examples of such propellants are water or carboxylic acids. Physical blowing agents are understood as compounds which are dissolved or emulsified in the starting materials of the polyurethane preparation and evaporate under the conditions of polyurethane formation. These are, for example, hydrocarbons, halogenated hydrocarbons and other compounds, for example perfluorinated alkanes, such as perfluorohexane, chlorofluorocarbons, and ethers, esters, ketones and / or acetals.

Preferably, the polyurethane systems according to the invention are water-driven. The proportion of water in water-driven polyurethane systems is from 0.1 to 2.0% by weight, more preferably from 0.2 to 1.5% by weight, in particular from 0.4 to 1.1% by weight, based on the total weight of components (b) to (f).

Examples of antioxidants, stabilizers against heat, light and / or UV radiation are stabilizers from the group of sterically hindered phenols, such as Cyanox 1790 ® from Cytec Industries INC, HALS stabilizers (hindered amine light stabilizer), triazines, benzophenones and the benzotriazoles. Examples of pigments and matting agents are titanium dioxide, magnesium stearate, silicone oil, zinc oxide and barium sulfate. Examples of dyes are acid dyes and disperse dyes.

Furthermore, the present invention relates to a method for the production of polyurethane sandwich parts, wherein (i) a core layer and at least one reinforcing fiber layer are provided, (ii) a polyurethane reaction mixture is applied to the reinforcements (iii) the part of (ii) is in a mold and in the mold cures the polyurethane reaction mixture, (iv) the molding is removed from the mold and optionally reworked, the polyurethane reaction mixture being obtainable by mixing the components of a polyurethane system according to the invention.

Thermoformable polyurethane foams and paper, metal or plastic honeycombs are preferably used as material for the core layer. As a reinforcing fiber layer may preferably glass fiber mats, Glaserfaservliese, Glasfaserwirrlagen, glass fiber fabric, cut or ground glass or mineral fibers, natural fiber mats and knitted fabrics, cut natural fibers and fiber mats, - fleece and knitted fabric based on polymer, carbon or aramid fibers and their Mixtures are used. In this case, the reinforcing fiber layer can be applied to one side of the core layer as well as on both sides of the core layer.

Polyurethane reaction mixture obtainable by mixing components (a) to (f) of a polyurethane system according to the invention is applied to the sandwich semifinished product obtained in this way. This is preferably done by spraying the polyurethane reaction mixture. Preferably, the polyurethane reaction mixture of the invention has a viscosity at 25 ⁰ C 280-3000 mPas, especially sawn vorzugt 350-2000 mPas, directly after mixing to approximately 5-10 seconds after mixing, the viscosity increases sharply.

To prepare the polyurethane reaction mixture, the individual components of the polyurethane system according to the invention are mixed so that the isocyanate dex 80 to 200, in particular 90 to 150. In the context of the present invention, the isocyanate index is understood as meaning the stoichiometric ratio of isocyanate groups to isocyanate-reactive groups multiplied by 100. Isocyanate-reactive groups are understood to mean all isocyanate-reactive groups contained in the reaction mixture, but not the isocyanate group itself.

Subsequently, the raw sandwich part is placed in a mold and the polyurethane reaction mixture is cured. The mold temperature is less than 1 10 ⁰ C. Preferably, the shape Temperature 40 ~ 1 10 ⁰ C, preferably 50 to 100 ⁰ C and more preferably 65 to 90 ⁰ C.

Optionally, the raw sandwich parts are pressed together with a cover layer or a decorative layer. In this case, the cover layer or the decorative layer can be applied to one or both sides of the polyurethane sandwich part. Alternatively, the cover layer or the decorative layer can be applied after removal of the polyurethane sandwich part in a further working step. As a decorative layer in this case against a polyurethane impregnated barrier fabrics, compact or foamed plastic films and spray or RIM skins made of polyurethane can be used. Suitable outer layers also include preformed materials suitable for outdoor applications, such as metal foils or sheets, and compact thermoplastic composites of PMMA (polymethyl methacrylate), ASA (acrylic ester modified styrene-acrylonitrile terpolymer), PC (polycarbonate), PA (polyamide), PBT (polybutylene terephthalate) and / or PPO (polyphenylene oxide) in lacquered, paintable adjusted or colored form can be used. As cover layers it is likewise possible to use continuous or discontinuously produced cover layers based on polyurethane, melamine-phenol, phenol-formaldehyde, epoxy or unsaturated polyester resins.

A great advantage of the method according to the invention is that it is also possible to compress, by the reduced mold temperature, more temperature-sensitive decorative layers, such as PVC (polyvinyl chloride), TPU (thermoplastic polyurethane), polyesters and automotive carpet materials, together with the raw sandwich parts and not only in a subsequent one Step must be applied using an adhesive.

The polyurethane sandwich weights produced by a process according to the invention can be used, for example, as structural components or trim parts, in particular in the automobile industry, the furniture industry or the construction industry.

Optionally, the raw sandwich parts are trimmed during pressing over so-called dip or Pinchkanten, so that no further post-processing, such as punching or milling is more necessary.

In particular, when reactive chain extender (s) is used, in addition to the advantage of low processing temperature, polyurethane sandwich weights according to the invention are characterized by improved edge formation over parts which were produced without the use of reactive chain extenders (e) according to the invention. Also, when using reactive chain extender (s), the polyurethane reaction mixture penetrates less into the core layer, thus achieving material savings and lighter weight of the sandwich weights.

Also, the use of reactive chain extender (s) results in reduced equipment fouling in the production of polyurethane sandwich ware because the raw sandwich ware parts are less prone to drain.

The present invention will be illustrated by the following examples. Polyol 1: Polyether polyol of OH number 555 ^{mg K0H} / _g , prepared by addition of PO to glycerol. Polyol 2: Polyether polyol of OH number 935 ^{mg K0H} / _g , prepared by addition of EO to trimethylolpropane. Polyol 3: Polyether polyol of OH number 400 ^{ms K0H} / _g , prepared by addition of

EO / PO on sucrose / diethylene glycol mixture. Stabilizer: Silicon Tegostab ^® B8443 stabilizer, GE Bayer Silicones Catalyst 1: N, N-bis (3-dimethylaminopropyl) -N-isopropanolamine catalyst, 2: adipic acid salt of N, N-bis (3-dimethylaminopropyl) -N-isopropanolamine in ethylene glycol

Catalyst 3: diethyltoluenediamine dye: Isopur ^® SU-12021/911 1, ISL-Chemie polyisocyanate: Lupranat M20W ^®, BASF SE

Catalyst 2 was prepared as follows:

900 g of adipic acid were weighed into a 5 l 4-necked round bottom flask and slurried in 2100 g of ethylene glycol. The whole was heated in an oil bath under reflux with stirring at 70 ⁰ C and then slowly added by means of a dropping funnel 1000 g of N, N-bis (3-dimethylaminopropyl) -N-isopropanolamine. During this time, the mixture continued to heat up and the adipic acid, which had only been slurried up to date, dissolved on reaction in ethylene glycol. It formed a reddish viscous liquid.

Recipe 1: (according to the invention)

The polyol mixture (polyols 1 to 3) has an average OH number of 600 ^m 9 κo ^H / _g Recipe 2: (comparison)

The polyol mixture (polyols 1 to 3) has an average OH number of 598 ^m 9 κo ^H / _g

Example 1: (according to the invention)

By means of a Hochdrucksprühanlage the polyol component and the isocyanate component were mixed together according to Recipe 1 and sprayed onto a prepared sandwich semi-finished product. A 17 mm thick expandable cardboard honeycomb was covered on both sides with 225 g / m ² random glass mat and sprayed with ~ 225 g / m ² PUR reaction mixture. Then the raw sandwich part was pressed in a 85 ° C hot mold to a component thickness of 15.5mm and demolded after 60s. After demolding, a polyurethane sandwich was obtained with very good edge formation, especially in sharp-edged areas.

Comparative Example 1

Starting from Formulation 2, the procedure was analogous to Example 1. Prior to loading into the mold, a significant portion of the sprayed reaction mixture drips off the raw sandwich. When demolding after 60 s, a quasi uncured molding was obtained.

Comparative Example 2:

Starting from Formulation 2, the procedure was analogous to Example 1, wherein at a mold temperature of 130 ⁰ C 60 s was pressed. Again, a significant portion of the sprayed reaction mixture dripped off the raw sandwich. After demoulding after 60 seconds, a fully cured polyurethane sandwich was obtained with significant defects at the edges.

Claims

claims

1. Use of a polyurethane system comprising a) polyisocyanates b) at least one isocyanate-reactive compound, c) at least one carboxylic acid salt of an amine catalyst, d) optionally further catalysts, e) optionally a reactive chain extender having at least two isocyanate-reactive groups, at least one opposite Isocyanate-reactive group is a free, primary Nhb group, and f) optionally further additives

for the production of polyurethane sandwich parts, wherein the polyurethane sandwich weights contain a core layer and the polyurethane sand weights obtained by compression of the core layer has a three-dimensional shape, and

wherein, based on one equivalent of amine of the amine catalyst, 0.5 to 1, 5 equivalents of acid groups of a carboxylic acid are included.

2. Use according to claim 1, characterized in that the carboxylic acid is a dicarboxylic acid of the general formula HOOC- (CH 2) _n -COOH, where n is an integer from 2 to 14.

3. Use according to claim 2, characterized in that the carboxylic acid is adipic acid.

4. Use according to one of claims 1 to 3, characterized in that the amine catalyst c) has at least one isocyanate-reactive group.

5. Use according to one of claims 1 to 3, characterized in that a reactive chain extender e) with 0.1 to 10 wt .-%, based on the total weight of components b) to f) is contained in the polyurethane system.

6. A process for the preparation of polyurethane sandwich parts, wherein i. presenting a core layer and at least one reinforcing fiber layer, ii. applying a polyurethane reaction mixture to the reinforcing fiber layer, iii. the part from ii. in a mold, the part of ii by pressing the core layer in the mold gives a three-dimensional shape and the polyurethane reaction mixture cures iv. removing the molding from the mold and reworking if necessary, wherein the polyurethane reaction mixture is obtainable by mixing the components of a polyurethane system according to claims 1 to 4.

7. The method according to claim 6, characterized in that the mold temperature is less than 1 10 ⁰ C.

8. The method according to claim 6 or 7, characterized in that the mold in step iii. contains a decorative element.

9. Polyurethane sandwich part, obtainable by a process according to one of claims 6 to 8.